Telephone-exchange system



R. D. CONWAY. TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED AUG.24, 1918.

1,383,789. Patented July 5, 1921.

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ROY n. CONWAY, or oHnrHAM, NEW JERSEY, As'srGN'oR 'ro wns rnn v nnno'rnr'o COMPANY, moonronnrnn, or NEW YORK, N. Y., A coarona'rron or new 7 'YORK.

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Specification of Letters Patent.

ilatented July 5, rear.

Application filed August 24, 1918. Serial No. 251,223.

To all whom it may concern:

Be it known thatl, Roy 1). CONWAY, a

citizen of the United States, residing at' Ghatham, in the county of Morris, State of New Jersey,. have invented certain new and useful In'iprovementsin Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention I relates to telephone exchange systems and more particularly to such systems in which connections are to be established between telephone lines termie nating respectively at manual and automatic exchanges. v

In some automatic exchange systems, especially those in which toll or long distance connections are established, certain incoming calls are receivedby an operator who establishes the connection with the desired subscribers line through the medium of a local trunkcircuit extending to the automatic switching apparatus. 5 V

V In systems of this nature it is desirable to provide means whereby the operator the manual exchange may signal the operator at the automatic exchange uponthe receipt of a call for connection with a line terminating at the automatic exchange and may receive from the automatic exchange characteristic signals indicating the occurrence of the various operations incident to this establishment of such a connection.

' The object of this invention is to provide an improved signaling'means for a trunk circuit interconnecting exchanges of this character.v To attain this object, in accordance with one feature of the invention, a trunk circuit extending between an automatic exchange and a manual exchange is provided withsignaling means responsive, to subscriber-controlled variations in the resistance of'a conductor associated with the local trunk circuit at the automatic exchange leading to the automatic switching apparatus. 1

In accordance with a second feature of the invention, a busy back circuitis provided at the automatic exchange to simulate the re-' sistance variations of the control conductor, caused by the repeated operations of the switchhook at the automatic subscribers station, so that when the busy back circuit is associated with the interexch'ange' trunk circuit, characteristic signaling is received at the manual switchboard to indicate the engaged condition ofthe calledline. v

Inaccordance with the third feature of .the invention, means is provided whereby the telephone set of the operator =at'the au I tomatjic exchange may be connected'with the interexchange trunk before the answer .of the called party,-.butfca1 1n0t be connected thereto afterthe called party has answered.

These and otherfeatures of the invention; not specifically mentioned above, will more fully appear from the following specificain which tion and the annexed drawing.

Figure ,1 shows diagrammatically one emloodi-ment of theinvention; Fig. 2 shows schematically certain portions of such embodiment; and Pi g. 3 illustrates a -modified form ofthe {system shown in F1g."1. i

Referring to Fig. VI of the accompanying a drawing a line 'Aextends to amanual exchange or switchboard X, and is'there connected inxany well-known manner with a cord circuit B. The cord circuit B may be employed to connect the telephone line A' with a trunk circuit Qextending from the; manual switchboard X to the automatic ex change or switchboard Y, where connection may be'made with a local'trunk circuit D,'

for extending the connection to the autoim a-tic line circuit E terminating at the switchboard Y. ".The apparatus shown at the left of the dotted line 2;? is located'at the manual switchboard X,-wl1ile that: at the right thereof is located at thefautomatic switchboard The apparatus'for connecting the local'trunk circuit '1) with the auto matio vline E, which is diagrammatically illustrated in the dotted rectangle 1. may be of the typedis closed in Patent No. l.287,483 granted to Samuel B. WVilliam's, J 1i, Aug;2l,

.1917. The apparatus shown atthe rightott' theverti'cal dotted line in Fig. 1 and' tha't shown inFig. 20f the-Williams patent, with the exception of the automatic line, maybe connected with. the three-conductor trunk circuit D'shown in Fig.1 of'the presentap pli-cation, in which case the slow release relay. 14 and the rotary and vertical magnets l 'l'and 23w'ould be controlled over the control-conductor 3 of the trunk circuit. D. A busy backcircuit F- shown as terminating in a jack 28 atthe switchboard Y 'is adapted foruse :withthe trunk circuitG in case the desired automatic line is'engagedp the schematic representation shown in Fig. 2 certain portions of the system illustrated by Fig. 1 are arranged in the conventional form of a VVheatstone bridge. tion of the trunk circuit C shown in the arrangement illustrated is adapted to replace that shown below the dotted lineage]: of Fig. 1, correspondingly numbered conductors 29, 30, 31 and 32 of each figure being connected together. c

It is thought that the invention will be more fully understood from thetollowing description of the operation of the system an idle trunk circuit C, operating the relays.

9 and 10, over a cir uit established from battery, through the left-hand windingo'f relay 10, left-handnormal contact of relay 5, the left-hand normal contact of relay 11, the ring'conductor of trunk circuit C, the ring contacts of jack 8 andhplug 7-,the winding of relay 9, the tip contactslot plu'g 7 and jack 8, the right-hand normal contact of relay '11, the right-hand normal contact of relay. v relay 10, to ground. Relay 9, in operating, prevents the lighting of supervisory lamp l2, andreray 10 in opendingcauses the lighting; 01 lamp over a circuit established from battery, through the. normal contact of relay 14, the alternate contact ofrelay and the lamp 13, to ground Upon observing the illumination of lamp 13, the operator at switchboard Y actuates the listen the sleeve contacts of plug 7 and aclt 8, and

the resistance 17, to ground. The closure of the alternate contacts of relay 11 connects the operators telephone set thereat, to

the trunk circuit C. Ascertaining that the connection is desired with the automatic line E, the key 15 is retained in an actuated position and the plug-18 is inserted into jack 19 of an idle local trunk D. Relay 20 is operated over a circuit'established from the In the modifica-- 5, and the ri rht-hand winding of battery which is connected to conductor 3 at the automatic switching apparatus 1, the contact or". relay 21, the sleeve contacts of jack 19 and plug 18, the upper alternate contact of key 15, the lower winding of relay 20, the winding of relay 16, and the contact of the dialing device '22, to ground. The closure of the lower contact of relay 2O short-circuits the series connection of the winding of relay 16 and the lower winding o1 relay 20. However, relay 20 is locked in an operated condition over a circuit extending from battery, through the lower alternate contactof key 15, and the upper contact and the upper winding of relay 20, to ground. The operator actuates the dialing device-22 in the usual manner to select the called line through the medium of the automatic switching apparatus (see the li illianis Patent No. 1,237 133).

After the necessary actuation of the dialing device 22, thelrey 15 is released which, by the opening of its, lower alternate contact, releases relays 20 and 11. Relay 14 is operated over a circuit established from the battery. connected to control conductor 3,

through the contact of relay 21, the sleeve contacts of jack 19 and plug 18, the normal contact ot'key the winding of relay 141, and the resistance 23, to ground. Relay 9 is also operated due to the closure of the normal contacts of relay 11 thereb extin- H However, lamp does not re-light since the closure of the normal contacts-oitrelay 11 likewise guishing supervisory lamp 12.

causes the lO-OIRI'fitl-Ollflll relay 10 over the circuit originally traced therefor. Belay 1 1- in operating. completes a l Vheatstone bl'lClfIG, the first. arm of which extends from battery, through the contact of relay 141- and resistance 25, while the second arm extends from the battery connected to conductor 3, through the contact of, relay 21, the sleeve contacts o't aclr iQand plug 18, the normal contact of irey 15 and the winding of? relay 1 1-. and the third and fourth arms of the bridge include groundedresistances 23 and 24;, respectively. T he resistances of the various arms of the bridge under the conditions existing at this period during the operation of the, system. are so adjusted that the bridge balanced and therefore no current flows through the winding of relay connected thereacross.

The answer of the called station on the automatic line E causes the operation of relay 21, over a circuit extending from bat cry, through the right-hand winding of relay 21, the automatic switching apparatus associated with the ring conductor of the local trunk D, the switch-hook contacts of the subscribers set connected with the line B, the automatic switching apparatus associated with the tip conductor of the local trunk D, and'the-le t-hancl winding of reresponse thereto from lay 21, to ground. The operation of relay 21 removes the normal short circuit existing around resistance 36, thereby including such resistance in series with the winding of re lay 14, so that the resistance of the second arm of the Wheatstone bridge is materially increased. The consequent unbalancing of the bridge causes a flow of current through the winding of relay 5. Relay 5 in operating opens the circuit traced for relay's 9 and 10,

to cause the releaseof relay 9, and the consequent l1 ghting of lamp 12, thereby notifying the operator V at switchboard X that the called party has answered. However, lamp 13 does not re-light dueto th'e locking of relay 10 over a circuit extending frombattery through the left-hand winding ofrelay 10, the alternate contact of relay 5, resistance 26, the alternate contact of relay 10 and the lamp 13, to ground. The resistance of this circuit is such that lamp'13 does not receive sufficient current to causeits lighting.

Relay QO is marginal in its operation, so that in case the key is actuatedafter the answer of the called party, relay will not operate overzthe circuit established from the battery connected to the conductor 3,

through the resistance 36, the sleeve contacts of jack 19 and plug 18, the upper. alternate contact of key 15, the lower winding of'relay 20, the winding of relay 16. and the contact of dialing device 22m ground. However, relay 16 will operate over this circuit.

Therefore, it is impossible to'operate relay 11 for reconnecting the operators telephone 'circuit at switchboardeY 'to the trunk circuit C after the answer of the called station. 1

Upon the termination 'o'fthe conversation, the called party of thesubstation on the line E, replaces the receiver thereat, causing the release of relay 21 which reestablishes the shunt. around resistance 36,'thereby again balancing the VVheatstone bridge andconse-f quently releasing relay 5 to-op'en the locking circuit of relay 10 and to reconnect such rclay in circuit with relay 9, as originally traced, and'causing theoperation of the latter mentioned relay, as well as .inalntainingrelay 10 inan operated condition; Lamp12 is extinguished by "the'operatio'nof relay 9, thereby furnishing a'di'scon'nect signal to the operator at switchboard X'who removes plug from jack 8, causing the release of relay 10 to light the lamp 13 over a circuit extending from battery, through the alternate contact of relay 14. :thenormal contact of relay 10, and lamp to ground. The illumination of lamp- 13 serves as a disconnect signal for the operator at switchboard Y and the subsequent'removal of'plug18 in I jack 19 'restores'all apparatus to normal. i

The operation of the system modified in aes' rda with. F 'gg s with ea relay 11 and theoperation of relay described for the "system shown Figs;

called line. I With the modified arrangement,

the release of key: 15 causes the'jrel'ease of lO'as and Quntil the key 15' is released after the 1 before,'buta circuit isestablished from the battery connected to the control conductor 3,;thr'0ugh the contact of relay 21," the sleeve contacts of jack l9 and plug 18, the.

"normal contactof key15,'the winding:of

relay 14, "and the -righthand"windingfof' I relay 27', to ground. As be fo're,f'relay 14L operates 4 immediately, extinguishing," lamp 13 :andcompleting a 'c'i rc uit from battery, through the alternate contact of relay 14,

and" the left hand winding of relay 27, to ground. .However,.relay 27 being differening of relay 27 in circuit therewith, receives a decreased amount of current, thereby operating relay 27" which, "as in the "case of relay .5, disconnects relay 10 from the trunk circuit C, to cause the releaseofsupervisory relay relay 1O islocked over a circuit extending from battery, through the left-hand windtially wound does notoperate under th'ese conditions. Upon the answerof the'called 3 station on theiautomatic line E, relay 21 foperatesto increase the sleeve resistance of the trunk D, so that the right-hand winding ofrelay 10, the; alternate contact of relay 27., resistance 26, the alternate contact of relay-1O and the lamp 13 to ground Lamp. 13 receives 'insufiicient current over I this circuitto cause'its lighting. Upon" the 'winding of*relay 27, causing therelease of suclirelay Relay ,9 operates,. rel ay1( is "maintained-in an operated" condition and the lamp 12 is extinguished as previouslydescribed in connection with the'releaseof relay 5.' Upon the removal-of plug7- from 'jack 8,1relay 10 is released and'lamp 13 is lighted as previously described, and the subtermination of the conversation atthe stasequent removal of plug 18 from jack19 v The busy'back circuit F shown Fig.1 is adapted for use either with the arrange 3, in case the desired automatic line is engaged. 1 If the operator at the automatic ,oauses all apparatustoreturn to normal,- 1 as before. i

i V '12 0 'ment shownin Fig. l-or as modified by Fig.

switchboard Y finds that the line E is en gaged, the plug 18 is inserted into jack28,

thereby operating relay 33 over circuit ex; tending from battery, through the operate ing and non-inductive windings of relay 3 3 inseries, the sleeve contacts "of jack 28 and plug18, where it joins theslee've 139 relay.

cuits traced for trunk circuit C in connecsleeve contact of jack 19, upon the answer of the called station on the automatic line E, and causes changes in the apparatus of the system similar to that resulting from the answer of the called party, including the lighting of supervisory lamp 12. The closure of the contact of relay 33 establishes a circuit from battery, through the contact of relay 83, the winding of relay 34% and interrupter 35, to ground. Relay 34: is operated and released in accordance with the interruptions produced by the interrupter 35. Upon each operation of relay 34: the non-inductive winding of relay 33 is shortcircuited, thereby reducing the resistance in circuit with the sleeve contact of plug 18 sufficiently to agree with that in circuit therewith when plug 18 is inserted into jack 19 rior to the answer of the called station. The responsive apparatus is therefore restored to the conditions existing immediately following the insertion of plug 18 into jack 28, and lamp 12 is extinguished. In this way lamp 12 is flashed in a characteristic manner under control of the constantly operating interrupter35, to notify the operator at switchboard X regarding the 1 engaged condition of the automatic line E.

However, due to the fact that relay 10 is maintained in an operated condition, lamp 13 remains extinguished untilplug 7 is re moved from jack 8 in response to the flashing of lamp 12.

It will be noted fromthe above description that signaling control means is provided for the trunk circuit, in either case, responsive to the variations produced in the control conductor, associated with the automatic,

exchange to produce suitable signals at the manual exchange.

What is claimed is: 1. A telephone exchange system comprising a trunk circuit extending from a first to a second central office, a line circuit terminatingat the second central office, a station thereon, a control conductor, switching means at the second central office controlled over the conductor and adapted to connect the trunk to the line, means responsive to the answer of the called station to cause a predetermined variation in the resistance of the conductor, a relay in the trunk circuit operating upon the connection of the trunk with the line and releasing upon the response of the called station, and a signaling device at the first central office controlled by the 2 A telephone exchange system comprising a trunk circuit extending from a first to a second central office, a telephone line terminating at the second central office, a station thereon, means to connect the trunk with the line, an operators telephone set at the second central office, switching means for connecting the telephone set with the trunk circuit prior to the response of the station on the connected line, and additional means controlled by the response ofthe station to prevent the connection of the telephone circuit to the trunk circuit during the continued connection of the trunk with the line.

3. A telephone exchange system comprising a trunk circuit extending from a first to a second central office, a line terminating at the second central ofiice, a station thereon, switching means for connecting the trunk with the line, an operators telephone set at .the second central office, operator-controlled switching means for connecting the operators telephone set to the trunk circuit prior to the response of the station,

determined variations. in the resistance of one arm of the bridge, and means IQSPOIISls'O to such variationsfor producing characteristicsignals at the first office.

5. A telephone exchange system comprising a trunkcirciiit extending from a first to a second central office, asignaling device at the first central office, an operators telephone and additional 7 means associated with the first-mentioned the operators telephone set to the set at the secondcentral office, means at the second central office for connectinga telephone set with the trunk circuit, a line terminating at the second central office, a station thereon, acontrol conductor, switching means at the second, central office controlled ,over the conductor and adapted to connect the trunk to the line, subscriber-controlled means responsive to the answer'of the called station to cause a predetermined variation in the resistance ofthe conductor,additional switching means at the second central office responsive to such variations for controlling the signaling device and for rendering the firstmentioned means ineffective.

6. A telephone exchange system comprising a trunk' circuit extending from a first to a second central office, a line terminating at the second central office, a station thereon, switching means for connecting the trunk to the line to call the station, a signaling device at the first central office, aW/Vheatstone bridgeassociated with the trunk circuit, a relay associated with the switching means, conductors between the contacts of said relay and the arms of the bridge, said bridge being unbalanced by the acuation of said relay upon the response of thecalled station, and a relay responsive to the unbalance of the bridge to control the signaling device.

7 A telephone exchange system comprising a trunk circuit extending from a first to a second central ofiice, a control circuit at the second central oifice, switching means for connecting the trunk with the control circuit, a Wheatstone bridge associated with the trunk circuit, a relay in the control circuit,

conductors between the contacts ofsaid relay and the arms of the bridge, said bridge I my name this 19th day ofAugustA.D.,1918.'

ROY D. OONVVAY. 

